Method and Apparatus for Providing Energy to Passive Tags in a Radio-frequency Identification System

ABSTRACT

A method and an apparatus for providing energy to passive tags in a radio-frequency identification system in which a radio-frequency identification system uses the passive tags, a reader/writer sends commands and continuous waves alternately during a communication process, and the tags can obtain energy from these signals sent by the reader/writer, wherein at least one period is selected from those periods for transmitting the continuous waves, and for the continuous wave transmitting signals during this period, an enhanced transmitting power is used, or a extended transmitting time is used, or during this period continuous waves are sent additionally to the passive tags by an independent energy supplying apparatus provided separately, so that the passive tags can obtain from the continuous waves during the selected period more energy for reading and/or writing, thereby improving the reliability of the reading and/or writing operations, and increasing the rewritable range of the radio-frequency identification system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of International Application No.PCT/EP2009/050944, filed on 28 Jan. 2009. Priority is claimed on ChineseApplication No. 200810004983.0, filed on 31 Jan. 2008. The entirecontent of both applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio-frequency identification (RFID)technology and, more particularly to a method and an apparatus forproviding energy to passive tags in a radio-frequency identificationsystem using such passive tags.

2. Description of the Related Art

Typically, a radio-frequency identification system comprises areader/writer (or interrogator) and the tags. In a radio-frequencyidentification system using passive tags, the energy of the passive tagsis obtained from the radio frequency waves sent by the reader/writer.For example, in the radio-frequency identification system based on EPCC1G2 (EPC Radio-Frequency Identity Protocols Class-1 Generation-2 UHFRFID Protocol for Communications at 860 MHz-960 MHz Version 1.0.9)protocol, the reader/writer sends commands and continuous wavesalternately during a communication process, the tags can obtain energyfrom the signals sent by the reader/writer.

The reading from and writing to the tags by the reader/writer are twomain operations in the radio-frequency identification system, where awriting operation is typically executed by the reader/writer after areading operation. When the reader/writer executes a writing operation,more energy will be consumed than a reading operation. Some tags whichare far away from the reader/writer obtain less energy. Consequently,these tags may not have enough energy to perform the reliable writingoperation after having executed a reading operation. Therefore, therange for performing a write operation of the reader/writer in theradio-frequency identification system using the passive tags is muchsmaller than the readable range, as shown in FIG. 1. This will limitmany applications of such radio-frequency identification systems.

In order to improve the reliability of the writing operation and toextend the rewritable range, it is necessary to provide more energy tothe passive tags in the radiofrequency identification system to performthe reliable writing operation.

In addition, when the reliability of the reading operation also needs tobe improved and the readable range also needs to be extended in theradio-frequency identification system, it is also necessary to providemore energy to the passive tags in the radio-frequency identificationsystem.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a method,an apparatus and a system for providing energy to passive tags in aradio-frequency identification system using the passive tags for thetags to obtain more energy, improve the reliability in executing thereading and/or writing operations, and to extend the read-only and/orthe rewritable range of the radio-frequency identification system.

This and other objects and advantages are achieved in accordance with afirst method for providing energy to a passive tag in a radio-frequencyidentification system, where a communication process of a reader/writerof the radio-frequency identification system comprises at least oneperiod for transmitting command signals and at least one period fortransmitting continuous waves, and the tag of the radio-frequencyidentification system obtains energy from the continuous waves. Thereader/writer selects at least one period from the period(s) fortransmitting the continuous waves as an enhanced period and thereader/writer then adjusts a gain for transmitting signals to send thecontinuous waves with an enhanced power during the enhanced period,and/or the reader/writer adjusts a time length for transmitting thecontinuous waves to the tag to send the continuous waves with anextended time length during the enhanced period.

In a preferred embodiment, the step for selecting the enhanced periodcomprises the reader/writer selecting at least one of a current or asubsequent period for transmitting the continuous waves as said enhancedperiod when the reader/writer detects that received signal strength forthe tag is less than a preset reference value for the received signalstrength.

In another preferred embodiment, the step for selecting the enhancedperiod comprises the reader/writer selecting at least one of a currentor a subsequent period for transmitting the continuous waves as saidenhanced period when a bit number to be written by the reader/writerinto the tag is greater than a preset reference value for the bitnumber.

In still another preferred embodiment, the enhanced period ispre-selected by the reader/writer.

Specifically, the enhanced transmitting power is greater than atransmitting power for transmitting the command signals.

Preferably, the enhanced transmitting power is a maximum allowabletransmitting power.

Preferably, the reader/writer further obtains relevant information foradjusting said gain through a training period.

The invention provides a reader/writer for realizing the disclosedembodiments of the method, comprising: a transmitting signal generatingunit for generating transmitting signals to be sent to the tag, wherethe transmitting signals comprise at least one period for transmittingthe command signals and at least one period for transmitting thecontinuous waves. A power adjusting unit is also provided for receivingthe transmitting signals provided by the transmitting signal generatingunit, and for performing a power adjustment to said transmitting signalsaccording to a set gain. The reader/writer further comprises an antennaunit for transmitting out the transmitting signals from the poweradjusting unit, a period selecting unit for selecting at least oneperiod from the period(s) for transmitting continuous waves as anenhanced period, a gain controlling unit, where the gain controllingunit is used for adjusting the gain of the power adjusting unit to makethe continuous waves reach an enhanced transmitting power during saidenhanced period and/or a time length setting unit for controlling thetime length of the transmitting signals of the transmitting signalgenerating unit to extend the time length of the above period fortransmitting the continuous waves during the enhanced period.

In a preferred embodiment, the reader/writer further comprises acondition judging unit for detecting the received signal strength forthe tag, where when the condition judging unit judges that the receivedsignal strength is less than a preset reference value for the receivedsignal strength, it triggers the period selecting unit to select atleast one period from the period(s) for transmitting the continuouswaves as the enhanced period.

In another preferred embodiment, the reader/writer further comprises acondition judging unit for detecting a bit number to be written to thetag where when the condition judging unit judges that the bit number isgreater than a preset reference value for the bit number, it triggersthe period selecting unit to select at least one period from theperiod(s) for transmitting the continuous waves as the enhanced period.

In preferred embodiments, the reader/writer also comprises a trainingunit for executing a training period and obtaining relevant informationto determine the gain set for the power adjusting unit during theenhanced period and to provide the determined gain to the gaincontrolling unit.

The present invention also provides an alternative method for providingenergy to a passive tag in the radio-frequency identification system,where one communication process of a reader/writer of theradio-frequency identification system comprises at least one period fortransmitting command signals and at least one period for transmittingcontinuous waves, and the tag of the radio-frequency identificationsystem obtains energy from the continuous wave signals, theradio-frequency identification system being provided with at least oneindependent energy supplying apparatus, the independent energy supplyingapparatus selecting from the period(s) for transmitting the continuouswaves at least one period as an enhanced period, the independent energysupplying apparatus monitoring the communication process of thereader/writer, and when it determines that it enters the enhancedperiod, the continuous waves are sent to the tag until the reader/writerstarts to send a next command.

In preferred embodiments, the independent energy supplying apparatus isprovided near the tag which is relatively far away from thereader/writer.

Preferably, the independent energy supplying apparatus is providedcorrespondingly according to a desired coverage range.

The present invention also provides an independent energy supplyingapparatus for achieving the method in accordance with the alternativeembodiment, comprising a period selecting unit for selecting at leastone period from the period(s) that a reader/writer sends the continuouswaves as an enhanced period, a period controlling unit for monitoringthe communication process of the reader/writer, transmitting out aninstruction for transmitting the continuous waves when it is determinedthat the reader/writer starts the enhanced period, and for transmittingout an instruction for stopping the transmitting of the continuous waveswhen it is determined that the reader/writer starts to send a nextcommand, and a continuous wave transmitting unit for transmitting thecontinuous waves to the tag upon receiving an instruction fortransmitting the continuous waves sent by the period controlling unituntil receiving the instruction for stopping the transmitting of thecontinuous waves.

In conventional radio-frequency identification systems using the passivetags, a reader/writer sends continuous waves in gaps betweentransmitting the command signals to provide energy to the tags, and thesame transmitting power is used both for transmitting the commandsignals and transmitting the continuous waves. An aspect of thedisclosed embodiments of the method of the invention is to enhance thetransmitting power of the continuous waves during the selected enhancedperiod, and as compared to the prior art methods, the contemplatedembodiment of the method of the invention can make the tags obtain moreenergy from the continuous waves for the reading and/or writingoperations, thereby improving the reliability of the reading and/orwriting operations, and extending the read only range and/or rewritablerange of the system. Moreover, the lower transmitting power is stillused to send the signals during other periods, which can avoid excessiveinterference to the operation of other reader/writers. The disclosedembodiments of the method of the invention do not increase the time fortransmitting the continuous waves. As a result, there is no extension ofthe time used for the reading and writing operations. If the enhancedtransmitting power is triggered only when a preset condition is met,then a large interference to the operation of other reader/writers canbe avoided while more power is provided to the tags to thereby improvethe reliability of the reading and/or writing operations.

In another embodiment of the disclosed method of the invention, in whichthe time for transmitting the continuous waves is extended in comparisonwith the prior art method, the presently contemplated embodiment of themethod can make the tags obtain, in a longer charging process, moreenergy for the writing operation, thereby improving the reliability ofthe reading and/or writing operations, and extending the read-only rangeand/or the rewritable range of the system. The contemplated embodimentof the method does not increase the transmitting power for thecontinuous waves, and therefore no additional interference to theoperation of other reader/writers is created. If the extendedtransmitting time is triggered only when a preset condition is met, thenthe efficiency of reading and/or writing operations can be improvedwhile more power is provided to the tags so as to improve thereliability of the reading and/or writing operations.

In the alternative embodiment of method of the present invention anadditional independent energy supplying apparatus is added, which can beeasily provided close to tags which are far away from the reader/writer,so as to supply additional energy to the tags with insufficient energyfor the reading and/or writing operations, thereby improving thereliability of the reading and writing operations, and extending theread-only range and/or the rewritable range of the system. Here, thereis no need for any further modifications to the existing radio-frequencyidentification systems, and therefore it can be easily applied to avariety of radio-frequency identification systems.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are designed solely for purposes of illustration and not as adefinition of the limits of the invention, for which reference should bemade to the appended claims. It should be further understood that thedrawings are not necessarily drawn to scale and that, unless otherwiseindicated, they are merely intended to conceptually illustrate thestructures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in detail herein below incombination with the drawings, in which:

FIG. 1 is an illustration of a schematic block diagram of read/writeranges in a radio-frequency identification system using passive tags;

FIG. 2 is an illustration of a schematic diagram of a process in which areader/writer performs a reading operation to a tag in accordance withan embodiment of the invention;

FIG. 3 is an illustration of a schematic block diagram of thereader/writer for realizing the method in accordance with an embodimentof the present invention;

FIG. 4 is an exemplary schematic block diagram for the implementation ofa power adjusting unit in accordance with an embodiment of theinvention;

FIG. 5 is an exemplary block diagram of a power adjusting unit inaccordance with an alternative embodiment;

FIG. 6 is an illustration of a schematic diagram of a process in which areader/writer performs a writing operation to a tag in accordance withan alternative embodiment of the present invention;

FIG. 7 is an illustration of a schematic block diagram of thereader/writer for realizing the method described in FIG. 6;

FIG. 8 is an illustration of a schematic block diagram of a transmittingsignal generating unit of the reader/writer in accordance with analternative embodiment of the present invention;

FIG. 9 is an illustration of a schematic block diagram of an independentenergy supplying apparatus in accordance with another embodiment of thepresent invention;

FIG. 10 is an illustration of a method in accordance with an embodimentof the invention; and

FIG. 11 is an illustration of a method in accordance with an alternativeembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an illustration of read/write ranges, whereas the inner circlerepresents a rewritable range I, the outer circle presents a read-onlyrange II and the area around the circles represents an unreadable rangeIII.

In accordance with the present invention, by way of the embodimentsdescribed below, energy is provided to passive tags in a radio-frequencyidentification system 1 using such passive tags 4 (hereinafter referredto as tags), so that the tags 4 obtain more energy for performing thereading and/or writing operations reliably. From the point of view of aradio-frequency identification system 1, this means an extended coveragerange.

In a first embodiment of the present invention the energy supply to thetags is increased by increasing the power strength in transmitting thecontinuous waves by a reader/writer.

FIG. 2 is an illustration of an exemplary process in which thereader/writer 2 performs a writing operation to a tag 4 after havingperformed a reading operation, where the example is based on the EPCC1G2 protocol. After the reader/writer 2 has performed the writingoperation to a set of tags 4, such as at time t₁, the tags 4 having beensuccessfully read are in an acknowledged state. At this time, thereader/writer 2 sends a Req_RN command 6 to a tag 4 in the acknowledgestate. The tag 4 generates and stores a new RN16 8, which can also becalled a handle and which handle is returned to the reader/writer 2 bybackscattering, and it turns to an open state or a secured state, suchas at time t₂. The reader/writer 2 then sends out one Req_RN command 6with the RN16 8, and the tag returns one cover code 7 correspondingly.Then, an access command 9, such as writing, can be executed by the tag.The tag 4 returns its handle to the reader/writer 2 to indicate asuccessful operation, or returns an error code to indicate anunsuccessful operation.

It can be seen from the above process that, in the prior art, thereader/writer 2 sends the command signals and the continuous waves 10(CW) during a communication process, and the tags 4 can obtain energyfrom the signals sent by the reader/writer 2, where the sametransmitting power is used in transmitting both the command signals andthe continuous waves 10. In fact, the tags 4 obtain energy mainly fromthe period for transmitting the continuous waves. As a result, inaccordance with the present invention, from those periods, such as theperiods t₂, t₄, t₆, for transmitting the continuous waves 10, thereader/writer 2 will select at least one period (e.g., the period t₂) asan enhanced period, the reader/writer 2 performs a power adjustment onthe transmitted signals to send out the transmitting signals during theenhanced period (i.e., continuous signals) with an enhanced transmittingpower, and the transmitting signals in the other periods, such as theperiods t₁, t₃, t₄, t₅, t₆, can be sent out with a transmitting powerdetermined by a conventional method. In the present invention, theenhanced transmitting power refers to a power greater than the powerused during the period for transmitting the command signals.

Therefore, by transmitting the continuous waves 10 at the enhancedtransmitting power during the enhanced period, the tags 4 can obtainmore energy from the continuous waves 10. While during the otherperiods, a smaller transmitting power such as the transmitting powerdetermined by conventional methods, is still used, which can avoid greatinterferences to the operation of the other reader/writers 2 nearby.Consequently, the tags 4 can obtain more energy for the writingoperation during the enhanced period.

Specifically, a maximum allowable power can be used as the enhancedtransmitting power during the period t₂. The maximum allowabletransmitting power is typically limited by the radio-related regulationsto avoid generating too much interference to other radio systems.

In a preferred embodiment for the adjustment, the reader/writer 2 can betriggered to select at least one period as the enhanced period when apreset condition is met, and the continuous waves 10 are sent out at theenhanced power during the period. As a result, the transmitting power ofthe continuous waves 10 is increased only when necessary, and theinterference to the operation of the other reader/writers 2 can bereduced as much as possible. The preset condition can comprise: thereceived signal strength indicator (RSSI) for the tags 4 of thereader/writer 2 is less than a preset reference value for the strengthof the received signal, or the bit number to be written into the tag 4is greater than a preset reference value for the bit number. Inaccordance with the invention, the reader/writer 2 detects the strengthof a received signal on which a writing operation needs to be performed,and then the strength of the received signal is compared with the presetreference value for the strength of the received signal, if the strengthof the received signal is less than the preset reference value for thereceived signal strength, then the preset condition is established asbeing met.

In an alternative embodiment, the reader/writer 2 detects the number ofbits sent to the tags 4 on which a writing operation needs to beperformed currently, and then the bit number is compared with a presetreference value for the bit number, if the bit number is greater thanthe preset reference value for the bit number, then the preset conditionis established as being met.

Preferably, the first period for transmitting the continuous waves 10after having determined that the preset condition is met is selected asan enhanced period, and this can promptly increase the energy supply tothe tags 4 with insufficient energy, thereby improving the reliabilityof the subsequent operation even more.

During an implementation, the above-mentioned object can be achieved byperforming a gain adjustment to the power for transmitting the signalsbefore transmitting the signals. In order to set the corresponding gainmore precisely, the reference information for gain adjustment can beobtained by one or more time segments for training purposes at thestarting stage of a communication process. The detailed process canrefer to the method of the prior art for obtaining the relevantinformation, for example, the signal power and for gain setting throughtraining periods, which will not be described in detail in the presentinvention.

In accordance with the contemplated embodiment, as an example, only oneperiod t₂ is selected to enhance the transmitting power of thecontinuous waves 10. In an alternative embodiment, more than one period(for example, the periods t₂, t₄) can also be selected to enhance thetransmitting power of the continuous waves 10. It is better to selectthe number of the enhanced periods according to the specific needs forenergy by the tag's writing operation, so as to achieve better effects.

FIG. 3 is an illustration of a schematic block diagram of thereader/writer 2 for realizing the method described in accordance with anembodiment of the present invention.

The reader/writer apparatus comprises a transmitting signal generatingunit U₁, a power adjusting unit U₂, an antenna unit U₃, a periodselecting unit U₄ and a gain controlling unit U₅.

Here, the transmitting signal generating unit U₁ generates modulatedtransmitting signals to be sent to the tags 4, and the transmittingsignals comprise at least one period for transmitting the commandsignals and at least one period for transmitting the continuous waves10. The power adjusting unit U₂ receives the transmitting signalsprovided by the transmitting signal generating unit U₁, and performs apower adjusting to the transmitting signals in accordance with the setgain. The antenna unit U₃ sends out the transmitting signals from saidpower adjusting unit U₂. The above-mentioned units basically correspondto units in an existing reader/writer; for their detailed implementationreference is to be made to the prior art.

The reader/writer 2 of the present invention, however is also providedwith a period selecting unit U₄, which is used for selecting at leastone period from the periods for transmitting continuous waves 10 as anenhanced period.

Moreover the reader/writer 2 of the present invention, is also providedwith a gain controlling unit U₅, which is used for adjusting the gainset for the power adjusting unit U₂, so as to allow the continuous waves10 to reach the enhanced power during the enhanced period, and to obtainthe transmitting power determined, for example, by the conventionalmethod during the other periods.

The specific mode for setting the gain controlling unit U₅ for the gaincan be as follows, for example, during a pre-selected enhanced period(e.g., the period t₂), a high gain is used to adjust the power of thecontinuous waves 10, so as to allow the transmitting power of thecontinuous waves 10 to reach the enhanced transmitting power, forexample, to reach the maximum allowable transmitting power. During theother periods, a low gain is used to adjust the power of thetransmitting signals to allow it to reach the transmitting powerdetermined by the conventional method. This setting mode is simple toimplement.

In addition, the period selecting unit U₄ can also select the enhancedperiod only when the preset condition is met and make the gaincontrolling unit U₅ adjust the set gain, so as to reduce as much aspossible the interference to the operation of the other reader/writers 2while providing enough energy to the tags 4. To achieve this purpose,the reader/writer 2 further comprises a condition judging unit U₆, whichis used for detecting the received signal strength for the tags 4, andwhen it is determined that the received signal strength is less than apreset reference value for the received signal strength, a notice thatthe preset condition has been met is sent to the period selecting unit.Alternatively, the condition judging unit U₆ detects the bit number tobe written into the tags 4, and when it is determined that the bitnumber is greater than a preset reference value for the bit number, anotice that the preset condition has been met is sent to the periodselecting unit U₄.

In addition, the reader/writer 2 can also further comprise a trainingunit U₇, which is used for executing a training period and for obtainingrelevant information, so as to determine a gain value set for the poweradjusting unit U₂ during the enhanced period and provide it to the gaincontrolling unit.

Two specific examples for realizing the power adjusting unit U₂ areshown in FIGS. 4 and 5.

The method for realizing the power adjusting unit U₂ of FIG. 4 is basedon a variable attenuator. The modulated transmitting signals generatedby the transmitting signal generating unit U₁ enter the power adjustingunit U₂. Here, after the transmitting signals have been amplified by apre-amplifier 11, they are sent to a variable attenuator 12, and afterhaving been attenuated by a variable attenuation value by the variableattenuator 12, they are sent into a power preamplifier 13 and a mainpower amplifier 14 to be amplified. Here, the gain given to thetransmitting signals by each amplifier is fixed. The final gainadjustment for the transmitting signals by the power adjusting unit U₂depends on the adjustment of the attenuation value of the variableattenuator. After this gain path, the continuous waves 10 of theenhanced period have their gain set by the gain controlling unit U₅ fromthe power adjusting unit U₂, and the transmitting power thereof canreach the enhanced transmitting power, where the transmitting signalsare sent out by the antenna unit U₃.

In the simplest case, the variable attenuator 12 has a high attenuationvalue corresponding to the low gain set by the gain controlling unit U₅,and has a low attenuation value corresponding to the high gain set bythe gain controlling unit U₅. When the gain controlling unit U₅ sets alow gain to the power adjusting unit U₂, the variable attenuator 12adopts the high attenuation value to attenuate the transmitting signalwith a greater attenuation. When the gain controlling unit U₅ sets ahigh gain, the variable attenuator 12 adopts the low attenuation valueto attenuate the transmitting signal with a smaller attenuation.

The method for realizing the power adjusting unit in FIG. 5 is based ona variable power amplifier. Here, modulated transmitting signalsgenerated by the transmitting signal generating unit U₁ enter the poweradjusting unit U₂, where, the transmitting signals are amplified by avariable power amplifier 21 and a fixed power amplifier 22. Here, thegain given to the transmitting signals by the fixed amplifier 22 isfixed, and the final gain adjustment given to the transmitting signalsby the power adjusting unit U₂ depends on the adjustment of theattenuation value of the variable attenuator 12. After this gain path,the continuous waves 10 of the enhanced period have the gain set forthem by the gain controlling unit U₅ from the power adjusting unit U₂,and the transmitting power thereof can reach the enhanced transmittingpower, by then the transmitting signals are sent out by the antenna unitU₃.

In the simplest case, the variable power amplifier 21 has a high gainvalue corresponding to the high gain set by the gain controlling unitU₅, and has a low gain value corresponding to the low gain set by thegain controlling unit U₅. When the gain controlling unit U5 sets a highgain to the power adjusting unit U₂, the variable power amplifier 21adopts the high attenuation value to set the transmitting signal with agreater gain; when the gain controlling unit U₅ sets a low gain, thevariable power amplifier 21 adopts the low gain value to set thetransmitting signal with a smaller gain.

In an alternative embodiment of the present invention, the energy supplyto the tags 4 is increased by extending the time for the reader/writer 2to transmit the continuous waves 10. FIG. 6 is a process illustratingthe alternative embodiment in accordance with the invention. Here,however, the process shown in FIG. 6 is basically the same as theprocess shown in FIG. 2, and redundant aspects will not be describedfurther. The differences between the process of FIG. 2 and FIG. 6 is inthe transmitting power and the transmitting time length for thecontinuous waves 10 during the period t₂.

As mentioned above, the reader/writer 2 will send the command signalsand the continuous waves 10 during the communication process, and thetags 4 can obtain energy from the signals sent by said reader/writer 2.In this embodiment, the time length for the reader/writer 2 to transmitthe continuous waves 10 to the tags 4 is extended, i.e., the energyobtained by the passive tags 4 can be increased correspondingly, therebyincreasing the rewritable range I. Specifically, the reader/writer 2selects at least one period, such as the period t₂, from those periods(i.e., the period t₂, t₄, t₆) for transmitting the continuous waves 10as the enhanced period, and the time length for transmitting the signalsto the tags 4 is adjusted, so as to send the continuous waves 10 withthe extended time length to the tags 4 during the enhanced period, andto send the signals with the time length determined by the conventionalmethod to the tags 4 during the other periods.

On the other hand, extending the time length for the reader/writer 2 totransmit the continuous waves 10 to the tags 4, will increase the timeused on the writing operation by the radio-frequency identificationsystem 1, thereby reducing the efficiency of the writing operation. Inorder to achieve a better balance between the rewritable range I and theefficiency of the writing operation, the reader/writer 2 can betriggered to select at least one period as the enhanced period when thepreset condition is met, and sends the continuous waves 10 with theextended time length during the period. Consequently, the time lengthfor the continuous waves 10 will be extended only when necessary, andtherefore the time spent on the writing operation can be reduced as muchas possible. Here, the preset condition comprises the received signalstrength from said reader/writer 2 to the tags 4 is less than a presetreference value for the received signal strength, or the bit number tobe written into the tags 4 by said reader/writer 2 is greater than apreset reference value for the bit number. In accordance with thedisclosed embodiments, the reader/writer 2 detects the received signalstrength indicator (RSSI) of the tag 4 to which a writing operation iscurrently performed, and the received signal strength is then comparedwith a preset reference value for the received signal strength, if saidreceived signal strength is less than the preset reference value for thereceived signal strength, the preset condition is then established asbeing met. Alternatively, the reader/writer 2 detects the number of bitsto be sent to the tag 4 to which a writing operation is performedcurrently, and the bit number is compared with a preset reference valuefor the bit number. Here, if the bit number is greater than the presetreference value for the bit number, then the preset condition isestablished as being met. Preferably, the first period for transmittingthe continuous waves 10 after having determined that the presetcondition is met is used as an enhanced period, and this can promptlyincrease the energy supply to the tags 4 with insufficient energy,thereby improving the reliability of the subsequent operation even more.

In accordance with the presently contemplated embodiment, as an example,only one period t₂ is selected to enhance the transmitting power of thecontinuous waves 10. Alternatively, more than one period, such as theperiods t₂, t₄, can also be selected to enhance the transmitting powerof the continuous waves 10. It is better to select the number of theenhanced periods according to the specific needs for energy by the tag'swriting operation, so as to achieve better effects.

FIG. 7 is an illustration of a reader/writer 2 for implementing themethod in accordance the alternative embodiment of the presentinvention.

In accordance with the contemplated embodiment, the reader/writer 2comprises a transmitting signal generating unit U₁, a power adjustingunit U₂, an antenna unit U₃, a period selecting unit U₄ and a timelength setting unit U₈. Here, the transmitting signal generating unit U₁generates transmitting signals to be sent to the tags 4, and thetransmitting signals comprise at least one period for transmitting thecommand signals and at least one period for transmitting the continuouswaves 10, and the transmitting signals are then output to the poweradjusting unit U₂. The power adjusting unit U₂ is used for performing apower adjustment to the transmitting signals provided by thetransmitting signal generating unit U₁ according to the set gain. Theantenna unit U₃ is used for transmitting the transmitting signals fromthe power adjusting unit U₂. The power adjusting U₂ unit and the antennaunit U₃ basically correspond to units of the existing reader/writer 2,and for their detailed realization reference is to be made to the priorart.

In accordance with the reader/writer 2 of the disclosed embodiments ofthe present invention, a period selecting unit U₄ is also provided inthe reader/writer 2, which is used for selecting at least one periodfrom the periods for transmitting continuous waves 10 as an enhancedperiod.

In the reader/writer 2 of the present disclosed embodiment of theinvention, a time length setting unit U₈ is also provided, which is usedfor controlling the time length of the transmitting signals of thetransmitting signal generating unit U₁, so as to extend the time lengthof the above-mentioned period for transmitting the continuous waves 10during said enhanced period.

In order to achieve a better balance between the rewritable range I andthe efficiency of the writing operation, the reader/writer 2 istriggered to select at least one period as the enhanced period when thepreset condition is met and the continuous waves 10 are sent out overthe extended time length during the period. To achieve this, thereader/writer 2 of the contemplated embodiment further comprises acondition judging unit U₆ for detecting the received signal strength forthe tag 4, where when the received signal strength is less adjusted tobe than a preset reference value for the received signal strength, theperiod selecting unit U₄ is triggered to select at least one period fromthe periods for transmitting the continuous waves 10 as an enhancedperiod. Alternatively, a condition judging unit U₆ is provided fordetecting a bit number to be written to the tag 4, where when thecondition judging unit U6 judges that the bit number is greater than apreset reference value for the bit number, it triggers the periodselecting unit U₄ to select at least one period from the periods fortransmitting the continuous waves 10 as an enhanced period.

As shown in FIG. 8, the transmitting signal generating unit U₁ canspecifically comprise a continuous wave sequence providing module M₁, acommand sequence providing module M₂, a sequence synthesizing module M₃and a modulating module M₄. Here, the continuous wave sequence providingmodule M₁ is used for providing a continuous wave sequence to be sent tothe tags 4, and for determining the time length of the continuous wavesequence according to the configuration of the time length setting unitU₈, so as to make it reach the time length set by the time lengthsetting unit U₈. Here, the so-called continuous wave sequence is thedigital sequence for generating the continuous waves 10. The commandsequence providing module M₂ is used for providing a command sequence tobe sent to the tags 4. Here, the so-called command sequence is thedigital sequence for generating the command signals. The sequencesynthesizing module M₃ is used for synthesizing the command sequence andthe continuous wave sequence into a digital sequence to be sent to thetags 4. The modulating module M₄ is used for modulating the digitalsequence output from the sequence synthesizing module, generating thetransmitting signals, and then for output to the power adjusting unitU₂.

In another embodiment of the present invention the energy supply to thetags 4 is increased by adding an independent energy supplying apparatus24 in the radio-frequency identification system 1 using the passive tags4. The main idea thereof is to dispose at least one independent energysupplying apparatus 24 in the radio-frequency identification system 1using the passive tags 4, which sends a segment of continuous wave 10with a certain length during the communication process of theradio-frequency identification system 1, so as to provide additionalenergy to the tags 4. The continuous waves 10 sent by the independentenergy supplying apparatus 24 should be in line with a maximum allowabletransmitting power limited by the radio-related regulations.

As mentioned above, the reader/writer 2 will send the command signalsand the continuous waves 10 during the communication process, and thetags 4 can obtain energy from the signals, i.e., the continuous waves10, sent by the reader/writer 2. In order to avoid the interference tothe communication of the radio-frequency identification system 1, it ispreferable for the independent power supplying apparatus 24 to selectthe periods of the reader/writer 2 to transmit the continuous waves 10to the tags 4, such as the period t₂, t₄, t₆ shown in FIG. 2, to send asegment of continuous wave 10 with a certain length to the tags 4, andthe selected period can be one (e.g., the period t₂ shown in FIG. 2), oralso more than one (e.g., the period t₂, t₄ as shown in FIG. 2), wherethe time length of this segment of the continuous wave 10 is the same asthe time length of the period for the reader/writer 2 to transmit thecontinuous waves 10 to the tags 4. Specific realization can be asfollows, the independent energy supplying apparatus 24 selects at leastone period from those periods for transmitting the continuous waves 10as an enhanced period, monitors the communication process of saidreader/writer 2, and when it is determined that it enters said enhancedperiod, it sends the continuous waves 10 to the tags 4 until it monitorsthat said reader/writer 2 starts to send a next command. Specifically,it is by monitoring that the reader/writer 2 has finished sending acommand that the entering point of the enhanced period is determined.The independent energy supplying apparatus can monitor the communicationprocess of the reader/writer 2 in a way similar to that for the tags 4to receive the signals sent by the reader/writer 2, but it does not needto return any information to the reader/writer 2.

The independent energy supplying apparatus 24 can be an independententity, and therefore it can be disposed near the tags 4 which are faraway from the reader/writer 2, and thus this can effectively improve thereliability of the writing operation of these tags 4. Preferably, morethan one independent energy supplying apparatus 24 can be disposed inthe radio-frequency identification system 1, and these independentenergy supplying apparatuses 24 can be correspondingly distributedaccording to a desired rewritable range I, thereby forming a distributedindependent energy supplying apparatus network. This can extend therewritable range I in a more targeted manner.

FIG. 9 is an illustration of a block schematic diagram of theindependent energy supplying apparatus 24 in accordance with analternative embodiment. The independent energy supplying apparatus 24comprises a period selecting unit U₄, a period controlling unit U₉, anda continuous wave transmitting unit U₁₀. Here, the period selecting unitU₄ is used for selecting at least one period from the periods fortransmitting the continuous waves 10 as the enhanced period. The periodcontrolling unit U₉ is used for monitoring the communication process ofthe reader/writer 2, when the starting of the enhanced period by thereader/writer 2 is determined, it transmits an instruction to send thecontinuous waves 10. When the beginning of transmission of a nextcommand by the reader/writer 2 is determined, it transmits aninstruction to stop transmitting the continuous waves 10. The continuouswave transmitting unit U₁₀ is used for transmitting the continuous waves10 to the tags 4 when it receives an instruction for transmitting thecontinuous waves 10 sent by the period controlling unit U₉, until itreceives the instruction to stop transmitting the continuous waves 10.

In each of the above described embodiments, the process in the stage ofthe writing operation is mainly exemplary embodiments for the presentinvention. Those skilled in the art can understand that if the enhancedperiod in the above embodiment is selected during the reading operation,then it can be an embodiment in the reading operation. When the presentinvention is applied to the reading operation, the specific methodthereof is similar to the above embodiments, but in the case of thereader/writer 2 not executing the writing operation, it is not by thenumber of written bits to determine whether to trigger to enhance thepower or extend the transmitting time. Therefore, for the embodimentapplied to the reading operation, no further redundant description is tobe made here.

Therefore, in the present disclosed embodiment invention, by enhancingthe transmitting power of certain or some transmitting periods orextending the transmitting time thereof during the reading and/orwriting operations, the energy supply to the tags 4 can be increased,thereby improving the reliability of the subsequent operations.

It can be seen from the above description that, in the implementation ofthe contemplated embodiments of the present invention, it is onlynecessary to make partial modification to the existing reader/writers 2,without any modifications to the tags 4, this being simple to implement.In one embodiment, it is only necessary to add a new apparatus in thesystem 1, without any modification to the entire radio-frequencyidentification system, and therefore it is convenient for use with avariety of radio-frequency identification systems.

FIG. 10 is an illustration of a method for providing energy to a passivetag in a radio-frequency identification system in which a communicationprocess of a reader/writer of said radiofrequency identification systemcomprises at least one period for transmitting command signals and atleast one period for transmitting continuous waves, and the passive tagin the radio-frequency identification system obtains energy from saidcontinuous waves. The method comprises selecting, by the reader/writer,at least one period from the at least one period for transmitting thecontinuous waves as an enhanced period, as indicated in step 1010. Atleast one of a gain for transmitting signals to send the continuouswaves with an enhanced transmission power during said enhanced periodand a time length for transmitting the continuous waves to the tag tosend the continuous waves with an extended time length during saidenhanced period are then adjusted by the reader/writer, as indicated instep 1020.

FIG. 11 is an illustration of an alternative method for providing energyto a passive tag in a radio-frequency identification system in which asingle communication process of a reader/writer of the radiofrequencyidentification system comprises at least one period for transmittingcommand signals and at least one period for transmitting continuouswaves, and the passive tag of the radio-frequency identification systemobtains energy from the continuous wave signals. The method comprisesproviding the radio-frequency identification system with at least oneindependent energy supplying apparatus, as indicated in step 1110. Atleast one period as an enhanced period from the at least one period fortransmitting the continuous waves is selected by the at least oneindependent energy supplying apparatus, as indicated in step 1120. Next,the single communication process of the reader/writer is monitored bythe at least one independent energy supplying apparatus and, when the atleast one independent energy supplying apparatus determines that saidenhanced period is entered, the continuous waves is sent to the passivetag until the reader/writer starts to send a next command, as indicatedin step 1130.

Thus, while there are shown, described and pointed out fundamental novelfeatures of the invention as applied to preferred embodiments thereof,it will be understood that various omissions and substitutions andchanges in the form and details of the illustrated apparatus, and in itsoperation, may be made by those skilled in the art without departingfrom the spirit of the invention. Moreover, it should be recognized thatstructures shown and/or described in connection with any disclosed formor embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice.

1-15. (canceled)
 16. A method for providing energy to a passive tag in aradio-frequency identification system, a communication process of areader/writer of said radiofrequency identification system comprises atleast one period for transmitting command signals and at least oneperiod for transmitting continuous waves, and the passive tag in saidradio-frequency identification system obtains energy from saidcontinuous waves, the method comprising: selecting, by thereader/writer, at least one period from the at least one period fortransmitting the continuous waves as an enhanced period; and adjusting,by the reader/writer, at least one of a gain for transmitting signals tosend the continuous waves with an enhanced transmission power duringsaid enhanced period and a time length for transmitting the continuouswaves to the tag to send the continuous waves with an extended timelength during said enhanced period.
 17. The method as claimed in claim16, wherein said selecting step comprises: selecting, by thereader/writer, at least one of a current or a subsequent period fortransmitting the continuous waves as said enhanced period when thereader/writer detects that a received signal strength for the tag isless than a preset reference value for the received signal strength. 18.The method as claimed in claim 16, wherein said selecting stepcomprises: selecting, by the reader/writer, at least one of a currentand a subsequent period for transmitting the continuous waves as saidenhanced period when a bit number to be written by the reader/writerinto the tag is greater than a preset reference value for the bitnumber.
 19. The method as claimed in claim 16, wherein the enhancedperiod is pre-selected by the reader/writer in said selecting step. 20.The method as claimed in claim 16, wherein the enhanced transmissionpower is greater than a transmission power for transmitting commandsignals.
 21. The method as claimed in claim 16, wherein the enhancedtransmission power is a maximum allowable transmission power.
 22. Themethod as claimed in claim 16, further comprising: performing, by thereader/writer, a training period to obtain relevant information foradjusting the gain.
 23. A reader/writer, comprising: a transmittingsignal generating unit configured to generate transmission signals to besent to a tag, said transmission signals comprising at least one periodfor transmitting command signals and at least one period fortransmitting continuous waves; a power adjusting unit configured toreceiving the transmitted signals provided by the transmission signalgenerating unit and configured to perform a power adjustment to thetransmitted signals in accordance with a set gain; an antenna unitconfigured to transmits out the transmitted signals from the poweradjusting unit; a period selecting unit configured to select at leastone period from said at least one period for transmitting continuouswaves as an enhanced period; and at least one of a gain controlling unitconfigured to adjust the gain of said power adjusting unit to set thecontinuous waves to an enhanced transmitting power during the enhancedperiod and a time length setting unit configured to control a timelength of the transmitted signals of said transmitting signal generatingunit to extend the time length of the at least one period fortransmitting the continuous waves during the enhanced period.
 24. Thereader/writer as claimed in claim 23, said reader/writer furthercomprising: a condition judging unit configured to detect a receivedsignal strength for the tag; wherein the condition judging unit triggersthe period selecting unit to select the enhanced period upon determiningthat the received signal strength is less than a preset reference valuefor the received signal strength.
 25. The reader/writer as claimed inclaim 23, wherein said reader/writer further comprises: a conditionjudging unit configured to detect a bit number to be written to the tag;wherein the condition judging unit triggers the period selecting unit toselect the enhanced period upon determining that the bit number isgreater than a preset reference value for the bit number.
 26. Thereader/writer as claimed in claim 23, wherein said reader/writer furthercomprises: a training unit configured to execute a training period andobtain relevant information to determine the gain to set for the poweradjusting unit during the enhanced period and to provide the set gain tothe gain controlling unit.
 27. The reader/writer as claimed in claim 24,wherein said reader/writer further comprises: a training unit configuredto execute a training period and obtain relevant information todetermine the gain to set for the power adjusting unit during theenhanced period and to provide the set gain to the gain controllingunit.
 28. The reader/writer as claimed in claim 25, wherein saidreader/writer further comprises: a training unit configured to execute atraining period and obtain relevant information to determine the gain toset for the power adjusting unit during the enhanced period and toprovide the set gain to the gain controlling unit.
 29. A method forproviding energy to a passive tag in a radio-frequency identificationsystem, a communication process of a reader/writer of saidradiofrequency identification system comprising at least one period fortransmitting command signals and at least one period for transmittingcontinuous waves, and the passive tag of said radio-frequencyidentification system obtaining energy from said continuous wavesignals, the method comprising: providing the radio-frequencyidentification system with at least one independent energy supplyingapparatus; selecting, by the at least one independent energy supplyingapparatus, at least one period as an enhanced period from the at leastone period for transmitting the continuous waves; and monitoring, by theat least one independent energy supplying apparatus, the communicationprocess of said reader/writer and, when the at least one independentenergy supplying apparatus determines that said enhanced period isentered, sending the continuous waves to the passive tag until saidreader/writer starts to send a next command.
 30. The method as claimedin claim 29, wherein the at least one independent energy supplyingapparatus is provided near the passive tag which is relatively far awayfrom the reader/writer.
 31. The method as claimed in claim 29, whereinthe at least one independent energy supplying apparatus iscorrespondingly provided in accordance with a desired coverage range.32. An independent energy supplying apparatus, comprising: a periodselecting unit configured to select at least one period from periods inwhich a reader/writer of a radio-frequency identification system sendscontinuous waves as an enhanced period; a period controlling unitconfigured to monitor a communication process of said reader/writer,transmit out an instruction to transmit the continuous waves upondetermining that the said reader/writer starts the enhanced period, andconfigured to transmit out an instruction to stop transmitting thecontinuous waves upon determining that the reader/writer starts to senda next command; and a continuous wave transmitting unit configured totransmit continuous waves to the passive tag upon receiving theinstruction to transmit the continuous waves sent by the periodcontrolling unit until receiving the instruction to stop transmit thecontinuous waves.